The Florida red tide, produced by the dinoflagellate Karen/a brevis, occurs almost annually and has[unreadable] adverse economic and health effects. Exposure of people to sea spray containing aerosolized K. brevis causes[unreadable] irritation of the eyes, nose, and throat, as well as bronchoconstriction in some individuals. In the first 5 years[unreadable] of the program project, we have developed methods to characterize red tide aerosol and to assess personal[unreadable] exposure. We have obtained information on the brevetoxin level produced by K. brevis on the beach and[unreadable] particle size distribution during exposure and non-exposure periods. We have developed dose estimates of[unreadable] the inhaled red tide aerosol and have showed an association of airborne brevetoxins to the observed[unreadable] respiratory effects.[unreadable] We also have shown that PbTx is a component of the marine aerosol generated from a wave-powered[unreadable] bubble mechanism. The concentration of PbTx aerosol during the red tide episodes is usually below 100[unreadable] ng/m3, which is sufficient to increase respiratory symptoms in human subjects in an occupational exposure[unreadable] study and studies involving asthma patients as described in the the Project by Flaming. The measured red tide[unreadable] aerosol particle size is in the coarse particle mode (>1 mu m in diameter) with a mass median aerodynamic[unreadable] diameter between 6 to 9.6 (mu m. The dose estimate based on the measured particle size showed a total[unreadable] deposition fraction of 82 to 89% in the human respiratory tract. The majority of inhaled red tide aerosol[unreadable] deposited in the upper airway (nasal, oral, pharynx and larynx region) with small but not insignificant deposition[unreadable] (3 to 7%) in the lower airways. The inhaled red tide aerosol has high deposition efficiency in the respiratory[unreadable] tract and the pattern of deposition would help to explain the observed respiratory symptoms. Our dose[unreadable] estimate indicates that several ng of deposited PbTx in a certain region of the human respiratory tract could be[unreadable] associated with observed symptoms in upper airway and/or lower airway systems. Our dose estimate shows[unreadable] that exposure to air concentrations as low as 3 to 5 ng/m3 may be sufficient to relate to upper airway[unreadable] symptoms, and higher PbTx concentrations of 30-40 ng/m3 may be required to cause lower airway symptoms[unreadable] for asthmatics. It also shows that brevetoxin is one of the most potent substances associated with human[unreadable] respiratory effects.[unreadable] Our colleagues at the Toxin Probes and Assays continue to separate and identify compounds from K. brevis[unreadable] cultures with structures related to the brevetoxin. These include the new brevetoxins (PbTx-11,12), and[unreadable] brevenals (antagonists of respiratory effects). As these new compounds are identified, we also need to[unreadable] quantify them in red tide aerosol samples obtained in the field study. In addition, our results show temporal[unreadable] variation of the PbTx profile during the sampling period as environmental conditions change. Therefore, it will[unreadable] be useful to improve the assessment of personal exposure and local deposition pattern in the upper airway to[unreadable] relate the observed respiratory symptoms with individual exposure.[unreadable] Based on this new information, we propose to continue studies to further characterize red tide aerosol[unreadable] and to investigate the means to predict and minimize red tide aerosol exposure. The overall objectives of our[unreadable] proposed study are (1) to identify red tide aerosol components that may have implications for respiratory heath[unreadable] effects including PbTxs, antagonists, and congeners, (2) to improve assessment of personal exposure and[unreadable] biomarkers for exposure, (3) to improve the understanding of marine aerosol formation and transport[unreadable] processes, and (4) to develop a model of the red tide aerosol in the affected area. Information gained from[unreadable] these studies will aid in evaluation of human risk associated with inhalation of red tide aerosols, and provide a[unreadable] means to predict red tide aerosol events, which may help to minimize future exposures to red tide aerosol.[unreadable]